Binaural recording and reproducing sound



July 1, 1930. 4 L. DE FOREST 1,769,907

BIN AURAL RECORDING AND REPRODUCING SOUND Filed Nov. 2'7. 1926 $0 I DOOUCIODD- ZZVVEZVT [as D 5,

$31350 inflow W1 8 v 7 I Patented July 1, 1930 UNITED STATES LEE DE FOREST, OF NEW YORK, N. Y., ASSIGNOB, BY MESNE ASSIGNMENTS, 'IO GEN- ERAI TALKING PICTURES CORPORATION, A CORPORATION OF DELAWARE IBINAUBAL RECORDING AND BEPBODUCING SOUND application filed November 27, 1928. Serial No- This invention relates in general-to talking)motion pictures.

ne of the objects of this invention is the provision of a new and novel apparatus for the reproduction of with motion pictures which are a faithful reproduction of the original sounds from which the are made.

nother object of this invention is the provision of a new and novel apparatus by means of which several sound records from.

the same source may be simultaneously recorded on the same or separate film negatives.

Another object of this invention is the construction of a single positive from this negative having thereon the two soundrecords in superimposed position and of a difierent color.

A further object of this invention is the provision of a new and novel arrangement of devices by means of which the sound may be reproduced at a plurality of points from the above described composite film.

A still further object of this invention is the provision of sound reproducing apparatus of this nature in which two photo-electric cells sensitive to light waves of difierent wave lengths are exposed to the light of different wave lengths coming from such a composite film.

A further object of this invention is to provide apparatus which is adapted to selectively disassociate the sound'records on such a composite film, so as to make themavailable for actuating photo-electric cells sensitive to light of the wave of bin-aural recording and reproducing sound. These and many other ob] cots are success- 7 fully sought through the agency of the method and apparatus to be described hereinafter.

This invention resides substantially in the method, combination, construction, arrangement andrelative location of parts orste s, as will be more clearly understood from t e following specification and drawings.

Referring to the drawings in which the same reference numerals will be used for sounds in connection slits with respect to the photographically recorded on of film,

microphones, two amplifiers, and two sources lengths of the light dis-:

parts in the difierent views to indicate the same or similar parts,

Fig. 1 is a diagrammatic view with the film gate in vertical cross-section of the apparatus for recording sound.-

'Fi 2 is a front elevational view of a film on w ich, the two records from the same source are to be recorded simultaneously showing the relation offithe recording film lm. Fig. 3 is a diagrammatic view showing the film cut partly in cross-section of apparatus employed by me for sound; and I Fig. 4 is a side elevational view of a composite film having the two superimposed sound recordsthereon.

In my 00- ending application, Ser. No. 121,679 filed uly 10, 1926, I have disclosed a system for recording simultaneously two distinct sound records from the same source and reproducing each by means of loud speaking devices located at different points with respect to a motion picture screen. The sound records which are'simultaneousl recorded from the same source of soun are made fromapparatus employing a microphone for each record located at different points 1 with respect tothe same source of sound. In that system two sound records are one for each source, using distinct of variable light; and in reproducing two sources of lig t and two photoelectric cells each with its own amplifier and loud speaker. As stated above, these loud speakers are arranged relative to'the screeen in positions correspondin in a manner to the original location of the two micropohones with respect to the sound source.

The method there'described requirestwo distinct sound records, preferably arran ed, one on either side of the motion picture Elm.

In the present apparatus, I employ a single composite film comprising two separate positives, each having thereon a separate sound record made from the same source thereby obtaining the benefits of so-called bin-aural reproduction without encroaching upon the the reproduction of 80 the same strip space of the film reserved for the picture in any greater degree than is at present required for the single sound record.

It has-been known thattwo sets of photographs can be printed on the same stri in different colors, for example in red and blue one on one side of the film and one on the other side, or both on the same side of the film, one color picture being superimposed upon the other, I utilize this principle in recording two sound records on the same strip, one in red and one in blue.

Referring to the drawings, there is shown in Fig. 1 at 1, a film gate having two fine slits 2 and 3 therein past which there is adapted to'be moved a motion picture film 4 in close proximity thereto. Mounted directly in back of the slits 2 and 3 are the light sources 5 and 6, which are respectively connected by means of the wires 9 and 10 to any suitable current amplifying devices 7 and 8, respectively. As one form of amplifier suitable for this purpose, I have indicated by the drawings a vacuum tube type. The amplifiers 7 and 8 are connected, respectively by means of cables 13 and 14 to the sound sensitivedevice or microphones 11 and 12. It will be apparent from this drawing and description when the microphones 11 and 12 are placed at the proper distance and at difi'er'ent points with respect to the same source that each light source will receive substantially the same currents representing the sounds from this source, but they will have some difierencesdue to the spacial relation which they bear to the sound source.

' It is important to note that the two slits 2 and 3 are not in vertical alignment with each other as will be apparent upon examination of Fig. 2. The two slits have been indicated by the black lines 2 and 3 on each side of the film 4:, so that the sound record will be made along each marginal edge of the film. For clarity, it may be stated again that these sound records will vary somewhat due to their different position of their'respective microphones, with respect to the sound source. While. I have shown the sound rec-. ords applied to the marginal edges of the film 4, itwill be apparent there would be no substantial deviation from this invention by recording them at other points on the film 4, or even on separate films.

It will be apparent that this apparatus is essentially adapted for recording sounds which emanate from a nu iber of separated sources. Thus, for instance, when recording music from a large orchestra it will be possible to get an approximately faithful record of all the instruments in the orchestra by employing two microphones. t is, of course, evident that a plurality of microphones could be utilized, and for instance, two microphones could be substituted for the microphone 11, or likewise two microphones for the microphone 12, the four microphones beget an even greater fidelity of rec-- particular point on the films where the records are printed, I have found that it is preferable to record them at one of the marginal edges thereof. It is important to note that these sound records are printed on their positives, so that when one is superimposed over the other, the two sound records may be juxtapositioned or juxtappposed, so that one lies directly above the other and not on opposite sides of the final positive, as was the ease with the original negative. One of these positivcs is then dyed one color and the other is dyed another. For instance, one may be dyed blue and the other red. The two dyed positives are then cemented together in such a manner that the red sound record lies exactly over the blue sound record in the manner indicated above. I have shown such a double positive in Fig. 4, in which the two films cemented together have been indicated at 15 and 16, it being intended that 15 represents the film which lies in back offilm 16. Thus. as described the film 15 would have the red sound record thereon.

For reproducing sound from such a composite record, I employ an apparatus of the type described in Fig. 3. At 17 and 18 are illustrated two constant light sources, such as incandescent lamps. The light from these, sources is transmitted through the lenses 19 and 20, respectively. and the fine slits 22 and 23 of the film gate 21. The composite film 15 and 16 moves over the surface of the gate, as shown in close proximity thereto. The light from the two sources 17 through the colored filters 2i and 25, respec tively. The colored filter in front of the slit 22 a red light filter, which as will be readily understood transmits light in the wave lengths representing the red light, and the filter 25 in front of the slit 23 is a blue filter which transmits or permits only blue light to pass. The red light transmitted by the filter 24 impinges upon a photoelectric cell of the thalolide type 26. which is especially sensitive to red or infra-red light. The blue light which is transmitted by the filter falls upon a photo-electric cell of the potassium mirror type 27, which is sensitive to greein and 18 pass electromagnetic sound reproducing units 34 and 35 of the loud speaking horns 36and 37, as shown. These horns are disposed with respect, to the motion picture screen 38 in the manner best suited to produce the effect that the sound is emanating fromtwo or more sources simulating the original sound sources.

I have indicated in Fig. 4, at 40 on the composite film 15, 16, the sound record, which is composed of the two so aratesound records,

as previously describe including red and shown on blue markings. In the reproducing apparatus, the disposition of the slits'22 and 23 are Fig.4 by the short heavy black lines, also represented by the reference 22 and 23.

It may be noticed that in this apparatus, as opposed to the recording apparatus of Fig. 1, that the two slits 22 and 23 are in vertical alignment and displaced vertically with respectto each other a distance equal to the vertical displacement between the two slits 2 and 3, so that sounds represented by the red and blue records will be simultaneously reroduced by the horns 26 and 37. It hardly need be stated here that if desired more than two loud speaking devices may be utilized and disposed'at any suitable points with respect to the screen 38. By loud speaker will'reproduce only the sound which is represented by this arrangement each ords on the evident that selectively disassociating colored superimposed are on the composite composite the two different I the two photo-electric cells sensitive to light of different 'wave lengths may be simultaneou'sly and individually actuated. w

changes in 5 0 relativearrangement of parts, as well as in for the purpose of illustrating It will be readily apparent to those-who are skilled in this art that there are many the details of construction an the steps of the method and relative arrangement, which will readily occur to them, an I do not,'thereiore, desire to be particularly limitedto the exact presented in this specification and drawings, the principles of my invention. I desire only to be limited as Ihave de- 'What I seek to secure by United States ILA talking motion picture film having two distinct photographic sound records, re-

cordedfrom the same source,

comprising two positive films secured together.

one of the sound'rec-j film. It will also be 1 I have provided apparatus for.

disclosure which I have 2. A talkin motion picture film having two distinct p corded from the same source, comprising two differently colored positive films permanently attached together.

3. A talking motion picture film having recorded from the two distinct sound'records otographicsonnd records re- I same source comprising two positive films same source united together with the two sound records superimposed.

.6. A talking motion picture film having two distinctsound' records recorded'from the same source, comprising two positive films each having a sound record from'the same source thereon and of a difierentcolor, said films being secured together with their sound records superimposed-on each other.-

7. A talking motion picture film having twodistinc'tsound records recorded from the same source comprising two positive films each having a sound record from the same source thereon, one film being blue and the other red, said films being secured together throughout their length with their. soun records superimposed.

8'. In a positive film having sound records thereon of the. same source, the combination of a blue and a red film united with their sound records disposed on each other.

'9.'The method of producing a bin-aural film having two sound records thereon com- 10. The methodof producing a bin-aural film having two sound records thereon comprising the stepsiof simultaneously making two recordsof the sound from a single source on a single negative film, printing and developing each sound record on a separate film, dyeing each positive a different color and securing the two positives together with their sound records lying directly over each other. 11. The method of producing-a bin-aural film having two sound records thereon comprising the steps of simultaneously making two records of the sound from a single source and developing each sound record on a separate film dyeing one of said positives red and the other blue and cementing said posicoloring each positive a'difierent hue and securing the two positives together.

, negative, printing relation, and thereafter their records superimfilm having two sound records thereon, comprising the steps of recording two parallel sound records simultaneously on the same different colored positives of each of said .records and cementing the positives together so that one of the positives of the records is superimposed on the other.

15. The method of producing a bin-aural film having two sound records thereon, comprising the steps of recording two parallel sound records simultaneously from the same source on the same negative, printing positives of each of said records, coloring each of said positives a different color, and cementing them together so that one of the positives of the records is superimposed on the other and longitudinally displaced therealong.

16. The method of bin-aural recording and reproducing of sound employing a film having two differently colored positive sound records from the same source superimposed one on the other, comprising the step of selectively dis-associating said records by means of color filters.

17 The method of bin-aural recording and reproducing of sound which consists in producing a bin-aural film having two sound records thereon, by recording two parallel sound records simultaneously from the same source on the same negative, printing positives of each of said records, coloring each of said positives with a different color, and cementing the positives together so that one of the positives of the records is superimposed on the other and subsequently selectively disassociating said records for purposes of re producing by means of color filters.

I 18. The method of bin-aural recording and reproducing of sound which consists in producing a bin-aural film having two sound records thereon, by simultaneously recording two parallel sound records from the same source on a. negative and mined longitudinally spaced apart relation thereon, printing positives of each of said records, dyeing each of said positives a different color, cementing the positives together so that one of them is superimposed upon the other in the same fixed predetermined longitudinal selectively disassociin a fixed predeter- LEE on FOREST.

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